chore: untitle first word of a string (#338)

strcase/goname.go

@@ -158,7 +158,7 @@ var customInitialisms = map[string][2]string{
 
 // TitleFirstWord upper case the first letter of a string.
 func TitleFirstWord(s string) string {
-	if len(s) == 0 {
+	if s == "" {
 		return s
 	}
 
@@ -168,6 +168,24 @@ func TitleFirstWord(s string) string {
 	return string(r)
 }
 
+// UntitleFirstWord lower case the first letter of a string.
+func UntitleFirstWord(s string) string {
+	if s == "" {
+		return s
+	}
+
+	r := []rune(s)
+
+	firstWord := strings.Split(s, " ")[0]
+	_, isCommonInitialism := commonInitialisms[firstWord]
+	_, isCustomInitialism := customInitialisms[firstWord]
+	if !isCommonInitialism && !isCustomInitialism {
+		r[0] = unicode.ToLower(r[0])
+	}
+
+	return string(r)
+}
+
 // lowerCaseFirstLetterOrAcronyms lower case the first letter of a string.
 func lowerCaseFirstLetterOrAcronyms(s string) string {
 	r := []rune(s)

strcase/goname_test.go

@@ -46,3 +46,21 @@ func TestTitleFirstWord(t *testing.T) {
 		}
 	}
 }
+
+func Test_UntitleFirstWord(t *testing.T) {
+	cases := [][]string{
+		{"", ""},
+		{"T", "t"},
+		{"UUID", "UUID"},
+		{"UUI", "uUI"},
+		{"TEST CASE", "tEST CASE"},
+	}
+	for _, i := range cases {
+		in := i[0]
+		out := i[1]
+		result := UntitleFirstWord(in)
+		if result != out {
+			t.Error("'" + result + "' != '" + out + "'")
+		}
+	}
+}